1. Field of the Invention
The present invention relates to a polypeptide having an enzymatic activity, more particularly, to a polypeptide having a .beta.-fructofuranosidase activity obtainable by the expression of a microbial gene.
2. Description of the Prior Art
Fructofuranosyl-transferred saccharides such as xylosylfructoside and lactosucrose, which have strong anticariogenic activities and growth promoting activities for bifid bacteria, are highlighted as the latest sweeteners substitutable for sucrose in the food and pharmaceutical industries. The fructofuranosyl-transferred saccharides are usually produced using .beta.-fructofuranosidases by contacting the enzymes with sucrose and amylaceous saccharides or lactose as materials. .beta.-Fructofuranosidases derived from microorganisms of the genera Bacillus and Arthrobacter have been widely used. However, the enzyme productivity of these microorganisms is relatively low, resulting in the requirement of a considerably large-scale culture of the microorganisms as a disadvantage.
The recent progress of recombinant DNA technology is outstanding. Even an enzyme, whose total amino acid sequence is not revealed, can be obtained with relative ease in a desired amount by preparing a recombinant DNA containing a DNA which encodes the enzyme, introducing the recombinant DNA into microorganisms or cells of plants and animals to obtain transformants, and culturing the transformants in nutrient culture media, if only a gene encoding the enzyme were isolated and the nucleotide sequence were decoded. In view of the foregoing, it is urgently required to obtain and reveal a gene encoding a .beta.-fructofuranosidase.